1. Field of the Invention
The present invention relates to chewing gum having a layered configuration wherein the outer layers are impervious to moisture and the inner layer contains all the formulated amounts of moisture sensitive components.
2. Description of the Prior Art
Chewing gum is made with various components such as L-aspartyl-L-phenylalanine methyl ester (aspartame or APM), an intense, artificial sweetener, and other flavorants, or combinations of components such as a food acid-CaCO.sub.3 filler combination, which are sensitive to moisture. A premature exposure of such components to deleterious amounts of moisture in the chewing gum product during its manufacture and/or shelf life causes undesirable effects, ie., a loss of sweetening effect when the APM reacts with water, or a reaction between the food acid and the CaCO.sub.3, or solvating effects on the stability of commonly used flavorants, such as fruit flavors.
The art has endeavored to meet the problems inherent in the use of these moisture sensitive materials in chewing gum products in various ways. In this regard it has been proposed, for example, to make the chewing gum under anhydrous conditions, as disclosed in U.S. Pat. No. 4,514,422; or to encapsulate, or fix, the APM or other moisture sensitive material, within a coating, encapsulating or absorbent material as disclosed, for example, in U.S. Pat. No. 4,384,004 and--PCT--International Patent Application WO 84/03201; or to otherwise formulate the chewing gum products in such a way that incompatible materials are either not used in a given formulation, or are maintained physically apart from each other therein, as disclosed, for example, in U.S. Pat. No. 4,374,858 wherein APM is placed on the outside or surface of the product.
In U.S. Pat. Nos. 1,771,981 and 1,771,982 there are disclosed various procedures and formulations for preparing layered chewing gum products. In each of these disclosures, however, the outer layers of the products are all formulated with moisture sensitive components, and, as such, such outer layers and ultimately, the unprotected inner layers, are readily susceptible to attack by moisture in the atmosphere, in the absence of the product being manufactured under anhydrous conditions, and being then packaged and stored in moisture impervious packaging or coating means.
Chewing gum also normally has about 2 to about 6 weight % of moisture formulated into the product. The moisture is part of the components normally added to the chewing gum formulations. Unless the loss of this moisture is prevented during the shelf life of the product, the product will harden and stale upon aging. This staling has usually been prevented in the prior art, by one or two ways. In one way products having a normal moisture content formulated therein are packaged in water impermeable packages that prevents the loss of moisture therefrom. In another way the normal moisture content of the product is lowered to anhydrous levels, i.e., of less than 2% and the product is formulated with relatively large amounts of a softening agent such as glycerine or propylene glycol. See in this regard U.S. Pat. No. 4,514,422 and International Patent application--PCT--WO 84/01693. However, the use of high amounts of these softening agents, which are highly hygroscopic, causes the chewing gum products in which they are used to deliquesce under even normal humidity conditions unless they are packaged in water impermeable packaging means.
Prior to the present invention, therefore, it has not been thought possible or feasible in the chewing gum art to readily render moisture sensitive materials insensitive to moisture by only employing such materials in a layer of chewing gum which is not readily accessible to ambient moisture, or to moisture normally present in a chewing gum formulation.
It has also not been thought feasible to avoid staling or hardening of chewing gum unless the product is either made with a normal moisture content and packaged in water impermeable packaging means or is made with a very low moisture content and is formulated with a high level of hygroscopic softening agents.
An object of the present invention, therefore, is to provide a new means for protecting moisture sensitive components of chewing gum from premature exposure to moisture during the shelf life thereof.
A further object of the present invention is to provide such means without the need for the use of additional materials, such as coating, etc. materials, beyond those normally needed for the formulation of the chewing gum products themselves.
A still further object of the present invention is to provide a non-staling chewing gum which is capable of maintaining its formulated moisture content with a low or non-existent content of hygroscopic softening agents.